US3516009A - High stability laser - Google Patents

High stability laser Download PDF

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Publication number
US3516009A
US3516009A US656588A US3516009DA US3516009A US 3516009 A US3516009 A US 3516009A US 656588 A US656588 A US 656588A US 3516009D A US3516009D A US 3516009DA US 3516009 A US3516009 A US 3516009A
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Prior art keywords
tube
discharge
discharge tube
cathode
laser
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Expired - Lifetime
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US656588A
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English (en)
Inventor
Morley S Lipsett
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Applied Biosystems Inc
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Perkin Elmer Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/02—Constructional details
    • H01S3/03—Constructional details of gas laser discharge tubes
    • H01S3/032—Constructional details of gas laser discharge tubes for confinement of the discharge, e.g. by special features of the discharge constricting tube
    • H01S3/0323—Constructional details of gas laser discharge tubes for confinement of the discharge, e.g. by special features of the discharge constricting tube by special features of the discharge constricting tube, e.g. capillary
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/02—Constructional details
    • H01S3/03—Constructional details of gas laser discharge tubes
    • H01S3/038—Electrodes, e.g. special shape, configuration or composition

Definitions

  • the cathode is mounted in the wall of the reservoir tube so that the ends of the discharge tube through which the radiation passes are shielded from sputtered cathode material.
  • the discharge passes from the cathode through a portion of the reservoir tube and into the discharge tube through an aperture.
  • Mirrors optically aligned with the discharge tube provide a resonant cavity Within which the laser beam is developed.
  • This invention relates to gas lasers and more particularly relates to an improved, high stability gas laser.
  • Typical gas lasers generally include a resonant cavity, a sealed enclosure containing an appropriate gas such as a mixture of helium and neon, and a discharge path in the enclosure, the major portion of which lies within the resonant cavity.
  • Anode and cathode means are provided to establish and maintain a discharge in the gas.
  • 'Ihe enclosure comprises a vitreous material and is hermetically sealed by windows angled so as to permit non-reflective transmission of radiation.
  • the resonant cavity is defined by a pair of mirrors between which radiation is reiiected to produce stimulated emission. An output beam is obtained by making one of the mirrors slightly transmissive.
  • Previous gas lasers particularly of the helium-neon type, have been subject to several diiculties.
  • the tubes have been of small diameter and therefore have been susceptible to vibration.
  • acoustic or mechanical shocks often cause the output wavelength to oscillate since tube vibration causes the angle of the end windows to vary and this affects the optical path length.
  • the danger of shock breakage is also increased.
  • Another diiiiculty is that helium can escape through the walls of the tube. Since the discharge tube must be small, the helium supply is small and the lifetime of the tube is limited.
  • the laser tube is not properly constructed, materials sputtered from the cathode during operation can collect on the end members of the discharge tube, thus decreasing the intensity of light obtainable from the device.
  • the present invention is directed to an improved gas laser construction which overcomes these difficulties and provides several additional advantages.
  • Another object of this invention is the provision of a new and improved laser construction which includes a large gas reservoir.
  • Another object of this invention is the provision of a 3 ,5 l 6 ,0.09 Patented June 2, 1970 ,Ice
  • an improved high stability laser which includes a gas enclosure comprising coaxially arranged discharge and reservoir tubes, the discharge tube being supported at each end by the reservoir tube.
  • An aperture is provided in the discharge tube so that the discharge runs from a cathode mounted in the reservoir tube through a portion of the reservoir tube, through the aperture and along the length of the discharge tube, terminating at an anode located adjacent one end of the discharge tube.
  • a gas supply is provided within the discharge and reservoir tubes, for example, the conventional mixture of helium and neon.
  • Hermetic enclosure of the gas is completed by providing the usual closure members such as Brewster windows adjacent the ends of the discharge tube which permit lossless transmission of radiation. Stimulated emission is achieved by providing a resonant cavity optically aligned with the discharge tube.
  • FIG. 1 is a cross-sectional view of a preferred embodiment of the present invention
  • FIG. 2 is a cross-sectional view of an alternative embodiment of this invention.
  • FIG. 3 is a cross-sectional view of another embodiment of this invention.
  • the novel laser illustrated in FIG. l comprises a gas enclosure 10 located within a resonant cavity defined by mirrors 11 and 12.
  • a suitable gas is provided within the enclosure 10 so that, upon the application of suiicient voltage between an anode electrode 13 and cathode 14 by power supply 15, a discharge is established and maintained along the path defined by the dash-dot line 16.
  • the conventional helium-neon gas mixture that is, He3 and Ne at a suitable pressure and mixed in an appropriate ratio.
  • a total pressure of 2 mm. of Hg and a ratio of 24 parts He3 to one part Ne is suitable. It is noted, however, that the laser construction described and claimed is generally applicable to other lgas mixtures.
  • the enclosure 10 usually of a vitreous material such as glass or ceramic, comprises a double tube construction including an inner discharge tube 17 and an outer reservoir tube 18.
  • the discharge tube 17 is a small diameter hollow cylinder located coaxially with the resonant cavity and is supported at each end by the large diameter reservoir tube 18.
  • the gas enclosure 10 is completed by a suitable end structure such as tubular extensions 19 and Brewster windows 20 which are sealed to the extensions 19 and angled to permit lossless transmission of the emitted radiation.
  • An aperture 21 is provided in the wall of the discharge tube to allow passage of the discharge between the anode and the cathode. Although this aperture may be located at any point inthe discharge tube, it is preferred that it be located on the opposite side of the discharge tube from the cathode. This limits the possibility that material sputtered from the cathode by the arc will enter the discharge tube. In conventional lasers, the sputtered material can enter the discharge tube where it collects on the end windows, thus reducing the output of the laser.
  • the two tubes are constructed from a single glass body and thus the support provided for tube 17 is rigid.
  • this invention is directed to the concept of supporting both ends of a restricted discharge tube within a second tube having a larger diameter and rigidly attaching elements which affect the optical path length to the larger diameter tube.
  • the use of the large reservoir tube stiffens the structure and reduces the danger of breakage and of wavelength oscillation due to vibration of the end members.
  • a flexible connection between tube 17 and tube 18 could be used as long as the Brewster windows 20 are attached to the tube 18.
  • a further benefit achieved by virtue of the construction described is that a large gas reservoir is provided within the tube 18.
  • the operational lifetime of the laser, before the gas supply is depleted due to gas clean-up, is increased. This is of particular importance when helium is involved since this gas can escape through the walls.
  • the construction described can conveniently be produced as a unitary glass member, thus facilitating the process of baking impurities from the walls during manufacture.
  • the present construction allows installation of the electrodes after the rest of the tube, including the precisely aligned end windows, has been completed without disturbing this alignment. This prevents contamination of the cathode.
  • the present invention avoids the necessity of clamping the discharge tube yby a metallic member which, although grounded, can produce oscillation in the discharge. In the case of the helium-neon laser, the large quantity of helium surrounding the discharge tube pro'vides rapid and uniform cooling of the discharge tube.
  • the length of the discharge tube may be approrimately three inches, the inner diameter may be about 2 mm. and the inner diameter of the reservoir tube may be about 2.5 cm.
  • a voltage of about 5 kilovolts is applied between the anode and the cathode and a heater voltage of approximately 6 volts is applied across the coil a.
  • An arc discharge is initiated through the gas where upon the voltage drops to approximately 1 kilovolt and the current stabilizes at about 3 milliamps.
  • the energy of the arc excites the helium which in turn collides with the neon, raising it to an excited energy level.
  • the neon then undergoes a radiative transmission to an intermediate energy level and return to the ground state upon collision with the wall of the discharge tube.
  • the radiation emitted by the neon is reected along the optical axis of the laser cavity between mirrors 11 and 12 as indicated by dotted line 22 and an output beam is extracted from one of the mirrors as indicated arrow 23.
  • FIG. 2 illustrates a device similar to that shown in FIG. l except that an additional element comprising a cylindrical shield 24 is now provided which extends from the end of the reservoir tube 18 adjacent aperture 21.
  • the shield is generally coaxial with the tubes 17 and 18 and extends therebetween.
  • the purpose of shield 24 is to provide an additional guard against the introduction of sputtered material from the cathode into the discharge tube.
  • the discharge path, indicated by dotted line 25, extends from the cathode through the reservoir tube, around the end of the shield 24 and then into the discharge tube via aperature 21. It is noted that other arrangements of the shield may be provided to serve the saine function.
  • FIG. 3 an alternative embodiment is llustrated which is structurally similar but which offers additional advantages in certain applications.
  • the discharge tube 17 is again mounted within and supported at both ends by the reservoir tube 18, Abut now the cathode structure 14 is centrally located along the length of the reservoir tube and the aperture 21 is centrally located along the length of the discharge tube 17.
  • Two anodes 13 are provided, one located in each tubular extension 19.
  • the discharge follows path 26 from the cathode to the aperture and then divides into two portions as indicated by lines 27 and 28 to the respective anodes 13.
  • the parameters given previously are generally repeated except that the tube is approximately twice as long.
  • the voltage applied is halved while the current is doubled.
  • a particular benefit is that the inductive effect of the current in the single anode situation is cancelled because there are two currents traveling in opposite directions.
  • a gas laser comprising:
  • a hermetically sealed enclosure within said cavity said enclosure comprising wall means defining a reservoir tube having opposite ends and end walls extending across and closing said ends;
  • a discharge tube mounted within and supported by the respective end walls of said reservoir tube, said discharge tube being optically aligned with said resonant cavity and defining a discharge path penetrating the respective end walls so that the interior 0f said discharge tube communicates with said tubular extensions;
  • anode means communicating with at least one of said tubular extensions
  • cathode means extending into said reservoir tube
  • aperture means in said discharge tube communicating with the interior of said reservoir tube located at a point on said discharge tube which is substantially diametrically opposed to the location of said cathode for permitting a discharge to be established between said anode means and said cathode means;
  • a laser as claimed in clairn 2 further comprising cylindrical shield means for causing a discharge to traverse a circuitous path between said anode means and said cathode means, said shield means being located intermediate said reservoir tube and said discharge tube and surrounding said aperture means.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Optics & Photonics (AREA)
  • Lasers (AREA)
US656588A 1967-07-27 1967-07-27 High stability laser Expired - Lifetime US3516009A (en)

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US65658867A 1967-07-27 1967-07-27

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US3516009A true US3516009A (en) 1970-06-02

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GB (1) GB1227968A (enExample)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3626325A (en) * 1969-11-10 1971-12-07 Britt Electronic Poducts Corp Pulsed gas laser with radiation cooling
US3721917A (en) * 1971-06-17 1973-03-20 V Fisher Gas-discharge devices for optical pumping of lasers
US3784927A (en) * 1971-06-11 1974-01-08 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Gas laser
US4065731A (en) * 1976-04-27 1977-12-27 Xerox Corporation Tandem laser assembly
US4190511A (en) * 1978-09-19 1980-02-26 Nippon Electric Co., Ltd. Method of manufacturing an internal mirror type gas laser tube
DE3103385A1 (de) * 1981-02-02 1982-08-26 Teldix Gmbh, 6900 Heidelberg Gaslaser
JPH028072U (enExample) * 1989-06-15 1990-01-18

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2561868A (en) * 1946-12-20 1951-07-24 Gen Electric Gaseous electric discharge lamp
US3390297A (en) * 1966-07-01 1968-06-25 Perkin Elmer Corp Shield for hollow cathode lamps
US3413568A (en) * 1965-06-22 1968-11-26 Bell Telephone Labor Inc Reversed axial magnetic fields in lasers

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2561868A (en) * 1946-12-20 1951-07-24 Gen Electric Gaseous electric discharge lamp
US3413568A (en) * 1965-06-22 1968-11-26 Bell Telephone Labor Inc Reversed axial magnetic fields in lasers
US3390297A (en) * 1966-07-01 1968-06-25 Perkin Elmer Corp Shield for hollow cathode lamps

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3626325A (en) * 1969-11-10 1971-12-07 Britt Electronic Poducts Corp Pulsed gas laser with radiation cooling
US3784927A (en) * 1971-06-11 1974-01-08 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Gas laser
US3721917A (en) * 1971-06-17 1973-03-20 V Fisher Gas-discharge devices for optical pumping of lasers
US4065731A (en) * 1976-04-27 1977-12-27 Xerox Corporation Tandem laser assembly
US4190511A (en) * 1978-09-19 1980-02-26 Nippon Electric Co., Ltd. Method of manufacturing an internal mirror type gas laser tube
DE3103385A1 (de) * 1981-02-02 1982-08-26 Teldix Gmbh, 6900 Heidelberg Gaslaser
JPH028072U (enExample) * 1989-06-15 1990-01-18

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Publication number Publication date
GB1227968A (enExample) 1971-04-15

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